For cosmetic purposes, colored contact lenses having one or more colorants dispersed in the lens or printed on the lens are in high demand. In general, there are two types of colored contact lenses. The first are contact lenses which use essentially transparent or semi-transparent enhancement colors that allow the color of the natural iris to show through but combine with that natural color to produce a new appearance. Such tinted lenses are typically used to turn a light eye (e.g., green) to a slightly different hue (e.g., aqua). This class of colored lenses may not be able to change an underlying dark colored, brown iris to blue. The second category is the class of opaque colored lenses having a continuous opaque pattern that fully covers the iris or having an intermittent opaque pattern that does not fully cover the iris. Opaque colored contact lenses can effectively and substantially modify the wearer's eye color. Colored contact lenses enhance the natural beauty of the eye, or provide unique patterns on the iris of the wearer, or provide non cosmetic patterns.
Colored contact lenses can be produced in a high volume manufacturing process involving cast-molding and printing on molded lenses or on molds for cast-molding contact lenses (U.S. Pat. No. 5,034,166 to Rawlings et al., herein incorporated by reference in its entirety). The large number of lenses which can be produced per minute necessitates the use of an automated inspection system to ensure not only the quality of a lens but also the quality of a colored print (or image) applied onto a lens.
In the contact lens manufacturing industry, it is well known that automated inspection of contact lenses offers the opportunity to reduce production costs while increasing product consistency. A number of automated inspection systems and methods have been developed for automatically inspecting non-colored contact lenses. Automated inspection of colored images (e.g., iris patterns, inversion marks, orientation marks, etc.) printed on lenses has been described in U.S. Pat. Nos. 6,047,082 and 6,471,891 (herein incorporated by references in their entireties). Recently, U.S. published patent application No. 2004/0114135 also discloses automated inspection of tinted ophthalmic parts. Each of these techniques for automated inspection of colored contact lenses is effective for reducing production costs and increasing product consistency. However, these techniques require that the center of a lens with a colored print applied thereon must be found in a digital image by algorithms prior to analyzing the quality of the pattern on the lens. The need to find the center of the lens in the digital image can be complicated and demand extensive computation if the digital image has a high resolution and/or three colors (red, green, and blue) captured therein. In addition, finding the center of the lens in the digital image may be complicated by the alternation in the configuration of the lens due to handling between removal from the mold and placement in a container suitable for inspection. Moreover, determination of the center of the lens in the digital image could be difficult if the print is non-symmetrical.
Therefore, there still exists a need for automated inspection of colored contact lenses.